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Global Challenges/Chemistry Solutions

New Fuels: An “artificial leaf” for turning sunlight into fuel

December 04, 2009

Scientists are working to create an
“artificial leaf” that imitates a living leaf’s
chemical photosynthesis process to
convert sunlight and water into a liquid
fuel like methanol for cars and trucks.Credit: National Aeronautics and Space
Administration (NASA)
(High-resolution version)

Summary

Scientists are making progress toward development of
an “artificial leaf” that mimics a real leaf’s chemical
magic with photosynthesis — but instead converts
sunlight and water into a liquid fuel such as methanol
for cars and trucks. That was among the topics at
the 1st Annual Chemical Sciences and Society
Symposium, initiated though the American Chemical
Society Committee on International Activities.

Leaves are a natural part of our everyday surroundings. But many people fail to appreciate their importance. Leaves provide us with shade, food, valuable medicines, breathtaking scenery, and even the oxygen we breathe.

Scientists are now making progress toward development of an “artificial leaf” that mimics a real leaf’s chemical magic with photosynthesis, but instead converts sunlight and water into a liquid fuel such as methanol for cars and trucks. That is among the conclusions in a new report from top authorities on solar energy who met at the 1st Annual Chemical Sciences and Society Symposium. The gathering launched a new effort to initiate international cooperation and innovative thinking on the global energy challenge.

The three-day symposium, which took place in Germany this past summer, included 30 chemists from China, Germany, Japan, the United Kingdom, and the United States. It was organized through a joint effort of the science and technology funding agencies and the chemical societies of each country, including the U.S. National Science Foundation and The American Chemical Society, the world’s largest scientific society.

A paper describing highlights of the symposium notes that the sun provides more energy to the Earth in an hour than the world consumes in a year. Compare that single hour to the one million years required for Earth to accumulate the same amount of energy in the form of fossil fuels. The paper notes that fossil fuels are not a sustainable resource and urges us to break our dependence on them. Solar energy is among the most promising alternatives.

The scientists pointed out during the meeting that plants use solar energy when they capture and convert sunlight into chemical fuel through photosynthesis. The process involves the conversion of water and carbon dioxide into sugars as well as oxygen and hydrogen. Scientists have been successful in mimicking this fuel-making process, termed artificial photosynthesis, but now must find ways to do so in ways that can be used commercially. Participants described progress toward this goal and the scientific challenges that must be met before solar can be a viable alternative to fossil fuels.

Highlights of the symposium include a talk by Kazunari Domen, Ph.D., of the University of Tokyo in Japan. Domen described his current research on developing more efficient and affordable catalysts for producing hydrogen using a new water-splitting technology called “photocatalytic overall water splitting.” The technology uses light-activated nanoparticles, each 1/50,000th the width of a human hair, to convert water to hydrogen and oxygen. He said that the technique is more efficient and less expensive than current technologies.

Julie Callahan, Ph.D., Image courtesy of American Chemical Society

Here is Dr. Domen to describe the process:

“Scientists have tried for many years to develop a way to split water molecules, similar to what leaves do during photosynthesis. My new process captures light and splits water using one device. It is one of the few water-splitting devices that uses visible light instead of ultraviolet light.”

“Current water-splitting systems have still only less than one percent solar energy conversion efficiency. We are trying to achieve a much higher efficiency of between 5 to 10 percent. If we can do that, then we will have an “artificial leaf” technology that is cheap and practical to use on a large scale.”

“We are very excited about the future our new “artificial leaf” technology for helping solve the world’s energy problems. My dream is to use the device to collect large amounts of solar energy in a desert area and then use that energy to develop chemical fuels such as methanol and ammonia. These fuels can then be used to power a car or generate electricity.”

Domen noted that the ultimate goal of artificial photosynthesis is to produce a liquid fuel, such as methanol or “wood alcohol.” Achieving this goal would fulfill the vision of creating an “artificial leaf” that not only splits water but uses the reaction products to create a more usable fuel, similar to what leaves do.

Julie Callahan, Ph.D., of the ACS Office of International Activities and principal investigator for the project, expressed hope that the solar energy symposium would be the first of an ongoing series of scientific symposia to tackle global challenges of the 21st century.

Here’s Dr. Callahan:

“Building on the success of this first symposium, we’re now gearing up for the future, convening top chemical scientists to address other, equally pressing global challenges. It is an exciting time to be a chemist.”

Smart chemists. Innovative thinking.

That’s the key to solving global challenges of the 21st Century. Be sure to check our other podcasts on fuels [Biofuels and The Sun and More]. Today’s podcast was written by Mark Sampson. I’m Adam Dylewski at the American Chemical Society in Washington.